The present disclosure relates generally to the field of aircraft navigation. More particularly, the disclosure relates to aircraft navigation using multiple radar antennas.
Conventional efforts in aircraft to implement tactical situation awareness displays and situational awareness displays with a track-up orientation for low-visibility surface operations are hampered by low quality navigation systems that support ground operations. Inertial Navigation Simulators (INS), Altitude Heading Reference Systems (AHRS), and Air Data Computers (ADC) do not provide velocity and/or heading data at speeds below about 40 or 50 knots (e.g., at taxiing speed). Magnetic compasses can provide heading information, but operate poorly during ground operations due to interference from ground infrastructure.
Velocity and track (heading) can be derived from GPS position data, but when the aircraft is stationary or performing low speed turning operations (e.g., turning 90 degrees from a hold line onto a runway) cannot be adequately measured by changes in aircraft position without using a Satellite Based Augmentation System (SBAS) to obtain additional messages broadcast by satellites or a Ground Based Augmentation System (GBAS) to obtain additional ground-based radio messages.
A GPS does provide accurate position information (latitude, longitude, and altitude). Aircraft velocity and track can be determined from a change in aircraft position over time. If more than one GPS antenna is installed, aircraft heading can be determined or derived from the difference between the two positions. However, the error in a standard positioning system is greater than the length of most aircraft. SBAS can bring the nominal error down to 7.5 meters 95% of the time and GBAS can bring the nominal error down to 2 meters 95% of the time, however, the smaller the aircraft, the closer the two antennas must be. For many aircraft, the distance between the two antennas is less than the error for standard GPS and not much bigger than the error for a system including an SBAS or GBAS. Further, GPS is subject to multi-path problems during ground operations.
Therefore, what is needed is a high quality navigation system and method for implementing with tactical situation awareness displays and situational awareness displays with a track-up orientation for low-visibility surface operations. What is also needed is a system and method for accurately providing velocity and heading information of an aircraft during low speed maneuvers or when stationary.